State House grime could get zapped by lasers
Cleaning would remove biofilm that has built up on the limestone
A dark film hangs over the Maryland State House, and it’s not the latest in partisan politics.
Over the past few years, the once gleaming white trim on the Annapolis capitol has developed a nasty case of grime, or as experts call it, biofilm.
The film — microorganisms that can include bacteria, algae and fungus — is the same culprit that plagues many of Washington’s marble and limestone monuments, and has frustrated curators because it seems to be an unstoppable force: You can clean it, scientists say, but you’ll never wipe it out.
At its meeting Thursday, the state Board of Public Works is expected to vote on a contract to clean black carbon and biofilm off the State House using a high-tech method: lasers.
The project, costing about $385,000, would be the most significant cleaning the facade has received in nearly two decades, said Nick Cavey, a spokesman for the state’s Department of General Services.
Biofilms are everywhere, said Elinor Pulcini, assistant research professor at Montana State University’s Center for Biofilm Engineering. The films live on river rocks, create the thin slime in a dog’s water bowl and contribute to the fuzzy stuff you feel on your teeth between brushing.
Once biofilms attach to a surface, they start colonizing. And as they spread, they produce extra substances — a coating that protects the microorganisms and keeps them from drying out in sunlight.
Cleaning biofilm can be complicated. In the past, many have used acids or blasting media to rid surfaces of the scum.
“You’d have to protect the surroundings, and if you would use blasting, you would have to collect everything” that came off, said Andrzej Dajnowski, head of the Chicago-based Conservation of Sculpture and Objects Studio.
Today, such methods could be considered harmful to the edifices and the environment.
Dajnowski’s firm uses laser equipment designed by his son’s company, GC Laser Systems. The devices are tuned to remove pollution without penetrating stone. Infrared light absorbs into the darker layer of gunk and “excites” the particles, Dajnowski said, evaporating the grime.
Crews follow up with distilled-water steam to lift stains.
The company recently used lasers to restore the marble facade of the U.S. Supreme Court. It also completed a lasercleaning test on a1,000-square-foot patch of the Jefferson Memorial dome, and has been hired by the state for a restoration job at the Fifth Regiment Armory in Baltimore.
If it is awarded the State House project, work would begin in the fall.
The Maryland State House, built in 1772, is the oldest state capitol in continuous use. The downtown Annapolis building is where the governor conducts business and the General Assembly meets for a 90-day session each year.
The side of the building that would receive the treatment was added between 1902 and 1906 and faces Lawyers Mall. Known as the “annex,” it’s the main public entrance for the State House.